1. Field of the Invention
The present invention broadly relates to an automatic transmission apparatus and, more particularly, to a support which is designed for supporting both the power transmission shaft and a hydraulic servo drum in the transmission apparatus and having internal oil passages for supply and discharge of the oil to and from the hydraulic servo drum.
2. Description of the Prior Art
A typical known automatic transmission apparatus has a power transmission shaft for transmitting the power, an annular hydraulic servo drum receiving a piston for driving a friction engagement means into and out of friction engagement, and a support having a tubular supporting portion which supports the transmission shaft at its inner peripheral surface while supporting at its outer peripheral surface the inner peripery of the hydraulic servo drum, the support being provided therein with oil passages through which oil is supplied to and discharged from the hydraulic servo drum. The hydraulic servo drum, transmission shaft and the support are made of aluminum in order to reduce the weight. The support has the oil supply and discharge passages formed in the outer peripheral surface thereof and designed for the supply and discharge of oil to and from the inner periphery of the hydraulic servo drum. The support also has an internal oil passage formed in the wall of the tubular supporting portion thereof. This internal oil passage has a radial oil passage formed from the outer peripheral surface of the tubular supporting portion so as not to reach the inner peripheral surface of the same, an axial oil passage formed from one axial end surface of the tubular supporting portion and communicating with the radial passage, the opening of the axial passage in the axial end of the tubular supporting portion being then plugged, and oil passages extending from the outer peripheral surface to the inner peripheral surface of the tubular supporting portion and aligned with the oil supplying and discharging holes formed in the inner periphery of the hydraulic servo drum. The tubular supporting portion has ring grooves for receiving seal rings which are adapted for preventing oil from leaking outside during the supply and discharge of the oil to and from the oil passage holes in the hydraulic servo drum from and to the opening of the passage holes opening in the outer peripheral surface of the tubular supporting portion.